To leach the metal, crushed ore must be dumped in relatively thin layers with a height of about 5 m to 10 m. Each of these layers consists of a plurality of high blocks arranged next to one another. In case of large leach pads, this dumping operation is carried out by a conveying and stacking system, comprising a movable conveyor belt system, traveling tripper and radial stacker. The progress of dumping is relatively great because of the low dumping height. This technology for filling up a high block makes it necessary to frequently move the belt and to transfer the devices of the system from one high block to the next. Some time is required for both operations, and the downtime will be longer.
The dumping operation is carried out in case of small leach pads by a large number of mobile conveyors without traveling gear, called grasshoppers, combined with a radial stacker on ramps. Such a device is shown in FIG. 1. The main assembly units of this device are a frame I, a non-driven chassis II and a conveyor belt III. This system is very flexible, but it has some drawbacks, which are related to the grasshoppers, on the one hand, and to the radial stacker used subsequently in such a conveyor system, on the other hand. The grasshoppers are relatively short with an overall length of 30 to 40 m because of the necessary mobility by means of an auxiliary transport device and, in the case of leach pads extending over a length of 1 km or more, they require a large number of such conveyors, between which the bulk material must be transferred from one conveyor to the next. In addition, a special device is needed for transfer from one site of use to the next. The radial stacker has two steerable radial caterpillars in the front area, by means of which it travels around the feed point located in the rear. This uninterrupted travel causes wear and disadvantageous compaction of the material develops at the same time under the caterpillars. Some of the above-mentioned drawbacks are avoided by the solution shown in the patent U.S. Pat. No. 6,782,993 B2. Longer grasshoppers, which can travel on four steerable and self-propelled caterpillars, are proposed in the invention described in that document. Due to the greater effective length of 70 m to 80 m, the number of grasshoppers and consequently the number of transfers are reduced. However, it is disadvantageous that the grasshoppers are used sometimes along and sometimes at right angles to the direction of travel. Each grasshopper is therefore equipped with two pairs of caterpillars, which can be swung by 180°. Since this swinging movement of the pairs of caterpillars cannot be brought about by an adjusting cylinder any longer, the two support chassis must be steered as a single two-caterpillar chassis by means of the caterpillar drives. This requires an additional effort for control and regulation and causes high chain tensions of the caterpillars. The radial stacker with the two steering caterpillars, which are always in operation, is unchanged. The drawbacks will thus persist as well.